Compacting uncured composite members on contoured mandrel surfaces

ABSTRACT

An uncured composite member is formed over a mandrel having a contour using a flexible compactor. Forming is performed outwardly from the apex of the contour.

RELATED PROVISIONAL APPLICATION

This application is related to and claims the benefit of priority ofprovisional U.S. Patent Application Ser. No. 61/813,821, filed Apr. 19,2013, entitled “Compacting Uncured Composite Members on ContouredMandrel Surfaces”, which is incorporated herein by reference.

BACKGROUND INFORMATION

1. Field

The present disclosure generally relates to processes for manufacturingcomposite structures, and deals more particularly with compaction ofcomposite laminate stringers on contoured mandrel surfaces.

2. Background

Elongate composite members such as stringers used in the aircraftindustry may be contoured in one or more planes along their length toconform to the curvature of a structure such as a fuselage skin.Contouring of a stringer may be accomplished using a compactor tocompact an uncured stringer layup against contoured surfaces of amandrel, such as a cure tool. Flexible compactors have been developedwhich flex or bend, allowing them to conform to contoured tool surfacesduring the compaction process.

Depending on the degree of tool contour, the uncured stinger layup maydevelop wrinkles as it is being compacted against the tool, particularlynear the center of curvature or greatest contour of the tool. Thiswrinkling occurs as a result of bending of the layers of compositematerial nearest the contoured tool surface, placing them incompression. Compression of the material in this manner causes excessmaterial to accumulate and bunch into wrinkles. Wrinkling may have anundesired effect on the performance of the cured stringer.

Accordingly, there is a need for a method of compacting uncuredcomposite members, such as stringers, on contoured tools, which controlsmaterial wrinkling. There is also a need for a method of compacting astringer on a cure tool using a flexible compactor that reduces the sizeof the wrinkles while distributing the wrinkles generally uniformlyalong the length of the stringer.

SUMMARY

Uncured composite members such as stringers may be bent to conform to ashaping mandrel such as a contoured cure tool, while avoiding theformation of relatively large wrinkles in the composite material. Anywrinkling of the composite material is limited to relatively smallwrinkles which are distributed generally uniformly along the contouredareas of the stringer. The avoidance of large wrinkles results instringers having improved structural performance and uniformity. Uniformdistribution of material wrinkling is achieved using an apex formingmethod and a flexible compactor. During the apex forming, the flexiblecompactor is used to place and bend the uncured stringer against acontoured tool surface, beginning at the apex of the contour, and movingoutwardly from the apex. The flexible compactor includes a series oftransverse kerfs therein into which excess composite material may bereceived during the compaction process to allow controlled formation ofrelatively small material wrinkles which do not materially affectstringer performance.

According to one disclosed embodiment, a method is provided ofcompacting an uncured composite member against a mandrel surface havinga contour. The method comprises adhering the uncured composite member toa compactor. The compactor is also used to align the uncured compositemember with the contour of the mandrel surface, and to bring the uncuredcomposite member initially into contact with the mandrel surface at theapex of the contour. The method includes forming the uncured compositemember over the contour of the mandrel surface, and the compactor isused to compact the uncured composite member against the mandrelsurface. Forming the uncured composite member may be performed by drapeforming the uncured composite member onto the mandrel surface. The drapeforming includes maintaining a substantially constant relationshipbetween ends of the uncured composite member and the mandrel surface asthe uncured composite member is being formed onto the mandrel surface.Forming the uncured composite member may be performed by lash forming.The forming includes reducing localized compressive forces in theuncured composite member adjacent the mandrel surface by inducing anS-shaped bend into the uncured composite member. Forming the uncuredcomposite member over the contour is performed after the uncuredcomposite member has been brought into initial contact with the mandrelsurface at the apex. The forming may be performed by forming the uncuredcomposite member onto the mandrel surface progressively outwardly alongthe uncured composite member from the apex. The uncured composite memberhas a preselected positional attitude when it is brought into initialcontact with the mandrel surface at the apex, and the positionalattitude of outer sections of the uncured composite member aremaintained substantially parallel to the preselected positional attitudeas the uncured composite member is being formed over the contour of themandrel surface. Forming the uncured composite member includes bendingthe uncured composite member to a progressively smaller radius ofcurvature. The method may further comprise distributing any wrinklesthat form in the uncured composite member during the forming by allowingmaterial in the uncured composite member to become compressed into kerfsin the compactor. The method may also comprise using the compactor toreduce wrinkling of the uncured composite member during forming byshifting the location of the neutral axis of the uncured compositemember.

According to another embodiment, a method is provided of controllingwrinkling of an uncured composite stringer during forming of thecomposite stringer over a contour of a mandrel surface, comprisingaligning the composite stringer with the apex of the contour of themandrel surface, and bringing the composite stringer into contact withthe mandrel surface at the apex. The composite stringer is formed fromthe apex down onto the mandrel surface. Forming the composite stringerfrom the apex includes bending the composite stringer down against themandrel surface and progressively outwardly from the apex. Forming thestringer includes maintaining a substantially constant relationshipbetween ends of the composite stringer and the mandrel surface, and maybe performed by one of drape forming and lash forming. The method mayfurther comprise installing a flexible compactor within the compositestringer, adhering the composite stringer to the compactor, and usingthe compactor to bring the composite stringer into contact with themandrel surface at the apex, and to form the composite stringer from theapex down onto the mandrel surface. Adhering the composite stringer tothe compactor is performed using a suction force. The stringer may beformed from the apex down onto the mandrel surface using a compactor.Wrinkling of the composite stringer is controlled by allowing materialof the composite stringer to be compressed into the compactor. Formingthe composite stringer from the apex down onto the mandrel surface isperformed using a compactor, and the compactor is used to encouragesubstantially uniform distribution of wrinkles in the compositestringer.

According to still another embodiment, a method is provided of formingan uncured composite member into a contoured groove in a cure tool. Themethod comprises adhering an uncured composite member to a compactor,and using the compactor to bring the uncured composite member intoinitial contact with the cure tool at an apex of a contour along thecontoured groove. The compactor is used to form the uncured compositemember down into and along the contoured groove and progressivelyoutwardly from the apex. The compactor is also used to distributewrinkles formed in the uncured composite member during forming of theuncured composite member down into and along the contoured groove. Usingthe compactor to form the uncured composite member is performed by oneof drape forming and lash forming.

The features, functions, and advantages can be achieved independently invarious embodiments of the present disclosure or may be combined in yetother embodiments in which further details can be seen with reference tothe following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the illustrativeembodiments are set forth in the appended claims. The illustrativeembodiments, however, as well as a preferred mode of use, furtherobjectives and advantages thereof, will best be understood by referenceto the following detailed description of an illustrative embodiment ofthe present disclosure when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is an illustration of a perspective view of a stringer contouredalong its length in an XZ plane.

FIG. 2 is an illustration of a cross-sectional view taken along the line2-2 in FIG. 1.

FIG. 3 is an illustration of a plan view of a stringer contoured alongits length in XY plane.

FIG. 4 is an illustration of a perspective view of a flexible compactorused to compact the stringers shown in FIGS. 1-3 against a cure tool.

FIG. 5 is an illustration of a longitudinal sectional view of thecompactor shown in FIG. 4, along with a stringer layup during compactionon a cure tool.

FIG. 6 is an illustration of the area designated as FIG. 6 in FIG. 5.

FIG. 7 is an illustration of a cross-sectional view showing thecompactor removing a stringer from a forming die.

FIG. 8 is an illustration of a cross-sectional view showing thecompactor indexed and aligned in readiness for forming the stringer intoa contoured cure tool cavity.

FIG. 9 is an illustration of a cross-sectional view showing the stringerhaving been formed into the contoured tool cavity, and a vacuum baghaving been installed in preparation for curing the stringer.

FIG. 10 is an illustration of a cross-sectional view showing thecompactor being lifted away from the stringer following curing.

FIG. 11 is an illustration of a perspective view of a portion of astringer, useful in explaining stresses on the stringer as it is beingformed into the cure tool.

FIG. 12 is an illustration of an end view of the stringer shown in FIG.11, showing the centroid and neutral axis of the stringer.

FIG. 13 is an illustration of a longitudinal side view of a stringer, inwhich the stringer has been brought into initial contact with the apexof a contoured mandrel surface in preparation for apex forming of thestringer.

FIG. 14 is an illustration of a diagram useful in explaining the apexforming method using a lash technique.

FIG. 15 is an illustration of the area designated as FIG. 15 in FIG. 14.

FIG. 16 is an illustration of a diagram useful in explaining the apexforming method using a draping technique.

FIG. 17 is an illustration showing the progressive shaping of thestringer during apex forming using the draping technique.

FIG. 18 is an illustration of a flow diagram of a method of fabricatinga stringer that includes use of the apex forming method.

FIG. 19 is an illustration of a flow diagram of aircraft production andservice methodology.

FIG. 20 is illustration of a block diagram of an aircraft.

DETAILED DESCRIPTION

The disclosed embodiments may be employed in the fabrication of anelongate, composite member that is contoured or curved in one or moreplanes. For example, referring to FIGS. 1 and 2, a composite fuselagestringer 30 is attached by any suitable means to a skin 32. The stringer30 possesses a hat shaped cross-sectional shape, comprising a cap 34,inclined sidewalls or webs 36, and outwardly turned, substantially flatflanges 38. Other cross sectional shapes are possible. In this example,the stringer 30 possesses a contour 42 lying in the XZ plane of anorthogonal coordinate system 40. The stringer 30 may comprise amulti-ply composite laminate, such as, without limitation, CFRP (carbonfiber reinforced plastic). It should be noted here that while a stringer30 has been illustrated, the disclosed embodiments may be employed tofabricate any of a variety of elongate, composite members that have oneor more curvatures in one or more planes.

As shown in FIG. 3, the stringer 30 may be contoured 42 in other planes,such as in the XY plane. In still other examples, the stringer 30 may becontoured in multiple planes. As will be discussed below in more detail,the stringer 30 is fabricated by laying up and forming prepreg to thedesired cross-sectional shape. A compactor 44 (FIG. 4) is used to formthe uncured stringer 30 into a contoured cure tool 68 (FIG. 8), and thencompact it during a cure cycle.

Referring now to FIG. 4, a compactor 44 may be used to assist intransporting, placing, forming and compacting the uncured stringer 30.The stringer 30 is releasably held or adhered to the compactor 44 usinga vacuum or suction force which will be discussed below. The compactor44 is generally semi-rigid, with a degree of flexibility that allows itto flex and conform to contoured tool surfaces 66 during placement andcompaction of the stringer 30. The compactor 44 may be constructed ofmaterials that are suitable for the application such as, withoutlimitation, a combination of CFRP and elastomer rubber. The compactor 44functions both as a device for installing and forming the stringer 30,and for controlling the cross-sectional shape of the formed stringer 30as it is being cured. The vacuum adherence of the stringer 30 to thecompactor 44 may reduce the risk of damage to the stringer 30 duringhandling, and controls the stringer 30 during installation onto acontoured mandrel surface such as a cure tool 68 (see FIG. 5).

The compactor 44 broadly comprises a hat section 46, a flange section 52and end walls 48 defining a generally open interior space 58. The hatsection 46 includes a plurality of longitudinally spaced, transverselyextending slits or kerfs 54 which provide the compactor 44 withflexibility, and allow air to be drawn into the open interior space 58.The vacuum fittings 50 in either, or both end walls 48, are adapted tobe coupled with a vacuum source (not shown) for evacuating the openinterior space 58. Although not shown in FIG. 4, the flange section 52may include one or more sections or joints along its length which areflexible, allowing the compactor 44 to flex in either or both of the XYand XZ planes.

The vacuum created within the open interior space 58 causes air to bedrawn in through the kerfs 54, producing a vacuum suction force 55. Thisvacuum suction force grips the uncured stringer 30, causing it to adhereand cling to the compactor 44 during the transport, placement andcompaction processes. More particularly, the cap 34 and the webs 36 ofthe stringer 30 are adhered to the hat section 46 of the compactor 44due to the vacuum suction force 55, while the flanges 38 of the stringer30 are in face-to-face contact with, but are not adhered to the flangesection 52 of the compactor 44. The vacuum adhesion of the stringer 30to the compactor 44 may also permit a more symmetrical distribution ofply wrinkling and gathering during stringer compaction, as will bediscussed below in greater detail. Moreover, the compactor 44 inducesacceptable wrinkles 60 a at the locations of the kerfs 54. “Acceptablewrinkles or wrinkling”, as used herein, refers to wrinkles which aresufficiently small in size and generally distributed along a sufficientlength such that they do not have a material impact of the performanceof the cured stinger 30 in-service, when placed under load.

Referring now to FIGS. 5 and 6, the compactor 44 may be used to form andcompact the uncured stringer onto a contoured surface 66 of a cure tool68 or similar contoured mandrel surface. In FIG. 5, the compactor 44 isshown having flexed in the XZ plane, to form the stringer 30 down ontothe contoured surface 66 of the cure tool 68. The vacuum adhesion of thestringer to the compactor 44 may aid in encouraging desired planar plyslippage between the outer plies (closest to the compactor 44) and theinner plies (closest to the cure tool surface 66) during this formingprocess. The method used to align, initially engage and then form thestringer 30 onto the contoured surface 66 will be hereinafter referredto as an “apex” forming method.

The apex forming method results in the distribution of excess stringermaterial 60 along the length of the stringer 30 facing the contouredtool surface 66. This distributed, excess stringer material 60 isallowed and encouraged to move partially into the kerfs 54 under thecompaction force applied to the stringer 30 by the compactor 44. Theexcess stringer material 60 which is under compression 78 (see FIG. 6),forms into a series of distributed, relatively small acceptable wrinkles60 a respectively within the kerfs 54. Because of the relatively smallsize of the wrinkles 60 a, and the fact that they are distributedgenerally uniformly along a sufficient the length of the stringer 30,stress concentrations within the cured stringer 30 under load, caused bymaterial wrinkling, are substantially reduced or eliminated. Thelocation and distribution of the wrinkles 60 a is dependent in part,upon the distance “D” between the kerfs 54. The distance “D” between thekerfs 54 may be generally constant along the length of the compactor 44to produce a substantially even distribution of the wrinkles 60 a.However, in some embodiments, it may be desirable to tailor thedistribution of the wrinkles 60 a such that they are not evenlydistributed. As the number of kerfs 54 provided in the compactor 44increases, the number of induced wrinkles likewise increases while thesize of each of the induced wrinkles decreases. Also, as the number ofkerfs increase, the ability of the compactor 44 to bend around toolsurfaces with tighter radii increases. Generally, it may be desirable toincrease the number of wrinkles 60 a while decreasing their size to thepoint that the wrinkles 60 a have a substantially negligible effect onthe performance of the stringer 30 when placed in service.

FIGS. 7-10 illustrate the sequential steps of forming, transporting,placing, forming and compacting the stringer 30 on the contoured surface66 of a cure tool 68 using the compactor 44. A prepreg layup may beformed into a desired hat shaped cross-section using any of varioustechniques, such as by stamp forming a flat layup (not shown) betweenmale and female dies (only the female die 64 is shown in FIG. 7), or bythe vacuum bag forming a flat layup onto a male die (not shown).

With the stringer 30 having been formed to the desired cross-sectionalshape, for example in a female die 64, the compactor 44 is placed in thestringer 30 such that the hat section 46 of the compactor 44 engageswebs 36 and the cap 34 of the stringer 30, and the flange section 38 ofthe compactor 44 overlies and engage the flanges 38 of the stringer 30.Depending upon the material and surface finish from which the compactor44 is formed, it may be necessary to install a release agent, such as apeel ply, between the compactor 44 and the stringer 30. For example, andwithout limitation a layer (not shown) of FEP (fluorinated ethylenepropylene) film may be taped to the compactor 44, covering the hatsection 46 of the compactor 44. Vertical slits (not shown) may be formedin the FEP film along the length of the compactor 44 to allow air toflow through the film and into the kerfs 54 of the compactor 44.

The stringer 30 and the compactor 44 may remain in the female die 64which may be used as a holding fixture to maintain the shape of thestringer 30 until the stringer 30 is ready to be removed and transportedfor placement. Optionally, the stringer 30 may be transferred to aholding fixture (not shown) until ready for transfer to a cure tool 68.In order to remove stringer 44 from the female die 64 (or an optionalholding fixture), a vacuum is drawn within the compactor 44 which drawsair in through the kerfs 54 (FIGS. 4-6) to create a suction force thatcauses the stringer 30 to adhere to and be gripped by the compactor 44.

With the stringer 30 adhered to the compactor along its length, thestringer 30 and compactor 44 behave as a single unit during subsequentprocessing, including forming onto the cure tool 68. In order to controlwrinkling of the stringer 30 during subsequent processing, the vacuumcausing the stringer 30 to adhere to the compactor 44 is maintaineduntil the stringer 30 has been formed onto the cure tool 68. In order toassure that the stringer 30 is not dis-bond from the compactor duringthe forming process, it may be necessary to adjust the forming raterelative to the amount of vacuum force applied to the stringer 30 toallow the stringer 30 to bend slowly along with bending of the compactor44. The vacuum-generated adhesion force adhering the stringer to thecompactor 44 must be stronger than the localized bending forces inducedin the stringer 30 in order to disperse the wrinkles 60 a along thestringer 30.

As shown in FIG. 7, with the stringer 30 adhered to the compactor 44,the compactor 44 is lifted along with the stringer 30 away from femaledie 64, and is used to transport the stringer 30 to a forming mandrelsuch as the cure tool 68 shown in FIG. 8. The cure tool 68 has contouredtool surfaces 66 forming a contoured tool cavity or groove 70. Thecontoured tool surfaces 66 are curved or contoured in at least one planeand substantially match the outer mold line (OML) surface (not shown) ofthe stringer 30.

The compactor 44 is used to place and form the stringer 30 onto thecontoured tool surfaces 66, along the length of the tool cavity 70, asshown in FIG. 8. As will be later discussed, the compactor 44 flexes toconform to the contoured surfaces 66 of the tool cavity 70, causing thestringer 30 to also be formed to the contoured shape of the tool cavity70. According to the disclosed apex method of forming, any wrinkling ofthe stringer 30 as it is being formed down into the contoured toolcavity 70 will be limited to relatively small scale “acceptable”wrinkles that are generally evenly distributed along the length of thestringer 30.

With the compactor 44 and the stringer 30 having been formed into thetool cavity 70, a vacuum bag (FIG. 9) is installed over the compactor 44and the stringer 30, and a vacuum is drawn in the bag 62 which, alongwith the compactor 44, compacts the layup 30 against the contoured toolsurfaces 66. Following compaction of the stringer 30, as shown in FIG.10, the compactor 44 is drawn away from the stringer 30. In someapplications, it may be desirable to apply a tackifier to the contouredtool surfaces 66 prior to installation of the stringer 30 and the curetool 68 in order to aid separation of the compactor 44 from the curedstringer 30 following curing. The stringer 30 may then be furtherprocessed. For example, fillers (not shown) may be installed in thestringer 30, one or more bladders (not shown) may be installed againstthe stringer 30, the stringer 30 may be attached to the skin 32 (FIG. 1)or other structure, and cured in an autoclave (not shown).

Attention is now directed to FIGS. 11 and 12 which illustrate stressesacting upon the stringer 30 when it is being formed onto contoured toolsurfaces 66 of a mandrel, such as the cure tool 68 previously described.The stringer 30 may be formed along a curvature (not shown in FIG. 11)in either the XY or the XZ planes. The geometry of the stringer 30 willdetermine which of these two planes has the most influence on theinstallation. Regardless of the particular cross-sectional geometry ofthe stringer 30, the stringer 30 possesses a neutral axis 80, and acentroid or geometric center 82. In FIG. 11, the location of the neutralaxis 80 is shown when forming the stringer 30 in the XY plane, whileFIG. 12 shows the location of the neutral axis 80 when forming thestringer 30 in the XZ plane.

Referring to FIG. 11, when the stringer 30 is formed along a curvaturein the XY plane, a bending moment M about the Z axis (axis of momentinduction) is produced which causes one side of the stringer 30 beplaced in tension 76, and the other side of the stringer 30 to be placedin compression 78. The neutral axis 80 shown in FIG. 12 is substantiallyperpendicular to the neutral axis 80 shown in FIG. 11 because the XZ andXY planes are perpendicular to each other, and likewise, the axes ofmomentum (the Y axis and the Z axis) are perpendicular to each other.The neutral axis 80 of the stringer 30 is a line or plane within thecross section of the stringer 30 at which no extension or compression ofthe stringer 30 occurs when it is bent, as occurs when the stringer 30is being formed into a tool cavity 70 (FIG. 8) that is curved in eitheror both of the XY and XZ planes. Referring to FIG. 12, when the stringer30 is formed along a curvature in the XZ plane, a bending moment M isproduced about the neutral axis 80 (the Y axis) which causes the area 81above the neutral axis 80 to be placed in tension, and the area 83 belowthe neutral axis 80 to be placed in compression.

The area 83 of the stringer 30 below the neutral axis 80 is the areamost likely to wrinkle because it is loaded into compression 78 as thestringer is being formed in either the XY or XZ planes. In contrast, thearea 81 that is in tension 76 during forming experiences a relativelysmall amount of strain, and thus normally does not wrinkle. Thecompression 78 below the neutral axis 80 causes a wrinkle 60 a (see FIG.6) to be formed in the stringer 30 as the stringer is being bent to aprogressively smaller radius of curvature during a forming process,because the same amount of stringer material is being conformed to asmaller radius within the area 83 below the neutral axis 80. In effect,the flexible compactor 44 functions to shift 85 (FIG. 12) the neutralaxis 80 downwardly, toward the cap 34 of the stringer 30. As a result ofthe neutral axis 80 being shifted 85 downwardly, the amount ofcompression in the area 83 below the neutral axis 80 within the stringer30 is reduced, and less wrinkling occurs in this area due to the reducedcompressive forces.

As previously discussed, apex forming is used to form the stringer 30into and along the contoured tool cavity 70 (FIG. 8) in order to controlwrinkling of the stringer 30 during the forming process. FIG. 13diagrammatically illustrates the apex forming method, generically. Acure tool 68 has a contoured tool surface 66 over which a substantiallystraight stringer 30 is to be formed by bending it to a progressivelysmaller radius of curvature until it conforms to the curvature of thecontoured tool surface 66. The straight stringer 30 comprises a stack ofsubstantially planar plies of uncured composite material such aspre-preg. The curvature of the contoured tool surface 66 has an apex 84which corresponds to the point of maximum curvature on tool surface 66.With the stringer 30 adhered to the compactor 44 (as shown in FIG. 8),the compactor 44 is used to align and index the stringer 30 relative tothe cure tool 68. The compactor 44 then initially brings the stringer 30into contact with the tool surface 66 at the apex 84. After this initialcontact at the apex 84, the stringer 30 is formed down 72 onto thecontoured tool surface 66 and into the tool cavity 70 (FIG. 8). Theparticular technique used to form the stringer 30 down onto thecontoured tool surface 66 after compaction at the apex 84 will dependupon whether the stringer 30 is being formed in the XY or the XZ plane,as will be discussed below. In applications where the tool surface 66has compound contours and it is necessary to form the stringer 30 inboth the XY and XZ planes, the compactor 44 may flex simultaneously inboth the XY and XZ planes. The compactor 44 may also form a torsionaltwist into the stringer 30 during the forming process, eitherindependently of, or in addition to flexing in either of the XY and XZplanes.

FIGS. 14 and 15 illustrate apex forming of a stringer 30 onto acontoured mandrel surface 66, such as that of a contoured cure tool 68,contoured in the XZ plane, using a lash forming technique. Thesequential positions and bend shapes of the stringer 30 are respectivelydesignated by the letters “A-D” in FIG. 14, and the individual laminateplies 90 of the stringer 30 are shown in FIG. 15. During this lashforming, the outer sections 74 not already in contact with the toolsurface 66 are held substantially parallel to the initial positionalattitude (designated by the letter “A”) of the stringer 30 when itinitially comes into contact with apex 84. Lash forming of the stringer30 in this manner induces an “S” bend 87 (see FIG. 15) into the stringer30. The formation of the “S” bend 87 shifts the location within thestringer 30 where tensile and compressive forces 76, 80 respectively areacting. Inducing an “S” bend 87 into the plies 90 of the stringer 30helps spread the wrinkling of the plies by reducing the localizedcompressive forces in the area adjacent the contoured tool surface 66where wrinkling may be expected to occur.

FIGS. 16 and 17 illustrate apex forming of a stringer 30 contoured inthe XY plane, using the compactor 44 to carry out a drape formingtechnique. The compactor is aligned and indexed such that it initiallybrings the stringer 30 into a first point of contact “A” correspondingto the apex 84 of the contoured tool surface 66. The stringer 30 is thenevenly draped onto the cure tool 68, into the contoured tool cavity 70(FIG. 8), by bending the stringer 30 about the apex 84. The letters “B”,“C”, “D” and “E” in FIG. 16 respectively represent simultaneous pointsof contact between the stringer 30 and the tool surface 66 as thebending process progresses. The corresponding bent positions of thestringer 30 are likewise designated in FIG. 17 by the letters “B′”,“C′”, “D′” and “E′”. During the bending process, the relationship of thedistances 92, 94 (FIG. 16) between the ends of the stringer 30 and thetool surface 66 is maintained substantially constant in order tomaintain an attitude of the stringer 30 that results in substantiallyeven bending about the apex 84. As previously noted, during this formingprocess, the vacuum adhesion of the stringer to the compactor 44 may aidin encouraging desired slippage between the planar plies of the stringer30.

Attention is now directed to FIG. 18 which broadly illustrates the stepsof a method of fabricating a contoured composite stringer 30 using theapex forming method and the compactor 44 described above. Beginning at96, a stringer charge is laid up and trimmed as necessary. The stringerlayup is then formed to the desired stringer cross-sectional shape atstep 98. Optionally, at step 100, a suitable perforated release filmsuch as FEP, may be placed over and adhered to the compacting surface ofa flexible compactor 44. The perforations allow vacuum airflow throughthe film and may be formed, for example and without limitation, bycreating a series of slits in the film. At step 102, the compactor 44 isinstalled into the cavity of the formed the stringer 30.

At 104, a vacuum is generated within the compactor 44 which adheres thestringer 30 to the compactor 44, effectively causing the compactor 44 togrip the stringer 30. At 106, the compactor 44 may be used to remove andtransport the stringer 30 to a contoured forming mandrel, which maycomprise a cure tool 68. As the stringer 30 is being removed andtransported, vacuum is held within the compactor 44 to maintainadherence between the compactor 44 and the stringer 30. At 108, the apex84 of the contoured mandrel or cure tool 68 is located, and may bemarked as a reference starting point to aid in the subsequent formingprocess. At step 110, the compactor 44 is used to align and bring thestringer 30 initially into contact with the contoured mandrel surface orcure tool 68, at the apex 84 of the contoured tool surface 66.

At 112, the compactor 44 is used to bend the stringer 30 down onto themandrel or cure tool surface 66, substantially evenly, outward from theapex, using either the drape forming or lash forming techniquepreviously described. During the bending process, the compactor 44 alongwith the stringer 30 flexes to conform to the contour of the mandrel ortool 68, causing the stringer material to wrinkle in a substantiallyeven distribution along the length of the stringer contour. At 114, theformed stringer 30 may be vacuum bagged and then compacted at roomtemperature using the compactor 44, during which the vacuum withincompactor 44 is maintained. At step 116, the stringer 30 is debagged,and the vacuum within the compactor 44 is released, allowing removal ofthe compactor 44 and the stringer 30 from the cure tool 68.

Embodiments of the disclosure may find use in a variety of potentialapplications, particularly in the transportation industry, including forexample, aerospace, marine, automotive applications and otherapplications where contoured elongate composite members, such asstringers, may be used. Thus, referring now to FIGS. 19 and 20,embodiments of the disclosure may be used in the context of an aircraftmanufacturing and service method 118 as shown in FIG. 19 and an aircraft120 as shown in FIG. 20. Aircraft applications of the disclosedembodiments may include, for example, without limitation, elongatestiffener members such as stringers used in the airframe 136 of theaircraft 120. During pre-production, exemplary method 118 may includespecification and design 122 of the aircraft 120 and materialprocurement 124. During production, component and subassemblymanufacturing 126 and system integration 128 of the aircraft 120 takesplace. Thereafter, the aircraft 120 may go through certification anddelivery 130 in order to be placed in service 132. While in service by acustomer, the aircraft 120 is scheduled for routine maintenance andservice 134, which may also include modification, reconfiguration,refurbishment, and so on.

Each of the processes of method 118 may be performed or carried out by asystem integrator, a third party, and/or an operator (e.g., a customer).For the purposes of this description, a system integrator may includewithout limitation any number of aircraft manufacturers and major-systemsubcontractors; a third party may include without limitation any numberof vendors, subcontractors, and suppliers; and an operator may be anairline, leasing company, military entity, service organization, and soon.

As shown in FIG. 20, the aircraft 120 produced by exemplary method 118may include an airframe 136 with a plurality of systems 138 and aninterior 140. Examples of high-level systems 138 include one or more ofa propulsion system 142, an electrical system 144, a hydraulic system146 and an environmental system 148. Any number of other systems may beincluded. Although an aerospace example is shown, the principles of thedisclosure may be applied to other industries, such as the marine andautomotive industries.

Systems and methods embodied herein may be employed during any one ormore of the stages of the production and service method 118. Forexample, components or subassemblies corresponding to production process126 may be fabricated or manufactured in a manner similar to componentsor subassemblies produced while the aircraft 120 is in service. Also,one or more apparatus embodiments, method embodiments, or a combinationthereof may be utilized during the production stages 126 and 128, forexample, by substantially expediting assembly of or reducing the cost ofan aircraft 120. Similarly, one or more of apparatus embodiments, methodembodiments, or a combination thereof may be utilized while the aircraft120 is in service, for example and without limitation, to maintenanceand service 134.

As used herein, the phrase “at least one of”, when used with a list ofitems, means different combinations of one or more of the listed itemsmay be used and only one of each item in the list may be needed. Forexample, “at least one of item A, item B, and item C” may include,without limitation, item A, item A and item B, or item B. This examplealso may include item A, item B, and item C or item B and item C. Theitem may be a particular object, thing, or a category. In other words,“at least one of” means any combination items and number of items may beused from the list but not all of the items in the list are required.

The description of the different illustrative embodiments has beenpresented for purposes of illustration and description, and is notintended to be exhaustive or limited to the embodiments in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art. Further, different illustrativeembodiments may provide different advantages as compared to otherillustrative embodiments. The embodiment or embodiments selected arechosen and described in order to best explain the principles of theembodiments, the practical application, and to enable others of ordinaryskill in the art to understand the disclosure for various embodimentswith various modifications as are suited to the particular usecontemplated.

What is claimed is:
 1. A method of compacting an uncured compositemember against a mandrel surface having a longitudinal contour andcuring, comprising: adhering the uncured composite member to a flexibleelongate compactor using a suction force; using the compactor to alignthe uncured composite member with the longitudinal contour of themandrel surface; using the compactor to bring the uncured compositemember initially into contact with the mandrel surface at an apex of thelongitudinal contour; forming the uncured composite member over thecontour of the mandrel surface outwardly from the apex; using thecompactor to compact the uncured composite member against the mandrelsurface; and curing the uncured composite member between the mandrelsurface and the compactor.
 2. The method of claim 1, further comprising:distributing any wrinkles that form in the uncured composite memberduring the forming by allowing material in the uncured composite memberto become compressed into kerfs in the compactor.
 3. The method of claim1, wherein the uncured composite member has a neutral axis and themethod further comprises: using the compactor to reduce wrinkling of theuncured composite member during forming by shifting the location of theneutral axis of the uncured composite member.
 4. The method of claim 1,wherein forming the uncured composite member includes using thecompactor to form a twist into the uncured composite member.
 5. Themethod of claim 1, wherein forming the uncured composite member isperformed by drape forming the uncured composite member onto the mandrelsurface.
 6. The method of claim 5, wherein the drape forming includesmaintaining a substantially constant relationship between ends of theuncured composite member and the mandrel surface as the uncuredcomposite member is being formed onto the mandrel surface.
 7. The methodof claim 1, wherein forming the uncured composite member is performed bylash forming.
 8. The method of claim 7, wherein the lash formingincludes reducing localized compressive forces in the uncured compositemember adjacent the mandrel surface by inducing an S-shaped bend intothe uncured composite member.
 9. The method of claim 1, wherein: theuncured composite member has a preselected positional attitude when itis brought into initial contact with the mandrel surface at the apex,and the positional attitude of outer sections of the uncured compositemember are maintained substantially parallel to the preselectedpositional attitude as the uncured composite member is being formed overthe contour of the mandrel surface.
 10. The method of claim 1, whereinforming the uncured composite member includes bending the uncuredcomposite member to a progressively smaller radius of curvature.
 11. Amethod of controlling wrinkling of an uncured composite member duringforming of a composite stringer over a longitudinal contour of a mandrelsurface and curing, comprising: installing a flexible elongate compactorwithin the uncured composite member; adhering the uncured compositemember to the compactor using a suction force; aligning the uncuredcomposite member with an apex of the longitudinal contour of the mandrelsurface; and, bringing the uncured composite member initially intocontact with the mandrel surface at the apex using the compactor;forming the uncured composite member from the apex down onto the mandrelsurface using the compactor to form an uncured composite stringer; andcuring the uncured composite stringer between the compactor and mandrelsurface.
 12. The method of claim 11, wherein forming the uncuredcomposite member from the apex includes bending the uncured compositemember down against the mandrel surface and progressively outwardly fromthe apex.
 13. The method of claim 11, wherein forming the uncuredcomposite member from the apex includes maintaining a substantiallyconstant relationship between ends of the uncured composite member andthe mandrel surface.
 14. The method of claim 11, wherein forming theuncured composite member is performed by one of drape forming and lashforming.
 15. The method of claim 11, wherein: wrinkling of the uncuredcomposite member is controlled by allowing material of the uncuredcomposite member to be compressed into the compactor.
 16. The method ofclaim 11, wherein: forming the uncured composite member from the apexdown onto the mandrel surface is performed using a compactor, and thecompactor is used to encourage substantially uniform distribution ofwrinkles in the uncured composite-member.
 17. A method of forming anuncured composite member into a contoured groove in a cure tool andcuring, comprising: adhering the uncured composite member to a flexibleelongate compactor using a suction force; using the compactor to bringthe uncured composite member into initial contact with the cure tool atan apex of a longitudinal contour along the contoured groove; using thecompactor to form the uncured composite member down into and along thecontoured groove and progressively outwardly from the apex; using thecompactor to distribute wrinkles formed in the uncured composite memberduring forming of the uncured composite member down into and along thecontoured groove; and curing the uncured composite member between thecure tool and the compactor.
 18. The method of claim 17, wherein usingthe compactor to form the uncured composite member is performed by oneof drape forming and lash forming.